Reel-to-Reel Laser Welding Methods and Devices in FPC Fabrication

ABSTRACT

A method of layering a layer of circuitry pattern to another layer of circuitry pattern during the manufacturing of a multilayer flexible printed circuit in a reel-to-reel machine. The method includes feeding both layers of circuitry pattern reel-to-reel into the machine, placing a layer of dielectric sheet material on the fly between the two layers of circuitry patterns reel-to-reel, followed by simultaneously passing the two layers of circuitry pattern and the dielectric sheet material under a laser scanner in the reel-to-reel machine to irradiate a laser beam on a layer of circuitry pattern to weld the two layers of circuitry patterns together.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to, and is a non-provisional patentapplication of U.S. Provisional Patent Application No. 62/903,343, filedon Sep. 20, 2019, now pending, which is hereby incorporated by referencein its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to renewable energy technologies ingeneral, and more specifically a FPC (flexible printed circuit)fabrication processes for the electric vehicle industry.

BACKGROUND OF THE DISCLOSURE

Known methods to produce a FPC (flexible printed circuit) include usinga gantry. Such manufacturing process is stop and go, and may requiremanual intervention.

There is a continuing need for faster ways to produce a FPC.

Known methods to produce a FPC include environmentally hazardousprocesses such as chemical etching and wasteful use of debonding sheets.

There is a continuing need for environmentally friendlier and/or morecost-effective ways to produce a FPC.

International patent application number WO20191507401, U.S. Pat. No.8,931,166 6, and China published patent application No. CN 203715762,all which are herein incorporated by reference in their entireties,disclose reel-to-reel manufacturing method for a variety of goods. Thesedisclosures, however, do not address all of the environment issues andcost-effectiveness issues.

U.S. Pat. No. 7,633,035 issued to Kirmeier, U.S. Pat. No. 8,510,934issued to Brand, and non-patent literature entitled Roll-to-RollProcessing of Film Substrates for Hybrid Integrated Flexible Electronics(Nagaraj an Palavesam et al 2018 Flex. Print. Electron. 3 014002) alsodisclosure related subject matters, all of which are herein incorporatedby reference in their entireties.

All referenced patents, applications and literatures are incorporatedherein by reference in their entireties. Furthermore, where a definitionor use of a term in a reference, which is incorporated by referenceherein, is inconsistent or contrary to the definition of that termprovided herein, the definition of that term provided herein applies andthe definition of that term in the reference does not apply. Thedisclosed embodiments may seek to satisfy one or more of theabove-mentioned needs. Although the present embodiments may obviate oneor more of the above-mentioned needs, it should be understood that someaspects of the embodiments might not necessarily obviate them.

BRIEF SUMMARY OF THE DISCLOSURE

In a general implementation, a reel-to-reel manufacturing method anddevice that produces flexible printed circuits (FPC) is disclosed. Thecontemplated manufacturing method can be implemented in a reel-to-reelmachine where a continuous metal foil is fed into the reel-to-reelmachine. The outcome at the trailing end of the reel-to-reel machine caninclude, but not limited to, 1) punched-out pieces of single-layerflexible printed circuits as an end product ready for industry use, 2)punched-out pieces of single-layer flexible printed circuits as anintermediary product ready to be layered with other pieces of flexibleprinted circuit to eventually produce multi-layer flexible printedcircuits for industry use, 3) a continuous sheet of multiple pieces offlexible printed circuits still attached to each other, wherein theentire sheet is an intermediary product ready to be layered up toanother sheet of similar intermediary product to eventually producemulti-layer flexible printed circuits, 4) punched-out pieces ofmulti-layer flexible printed circuits as the end product ready forindustry use.

In one aspect combinable with the general implementation, a novel laserablation process to create a circuitry pattern in a reel-to-reel processand/or within a reel-to-reel machine where a sheet material iscontinuously fed into the reel-to-reel machine is disclosed. The laserablation is contemplated to replace the need for chemical etching whichcan be costly and environmental hazardous. Contemplated laser ablationprocess eliminates the need to chemically wash away metal.

Generally, the fabrication process may start with 1) a metal foilalready on a UV debonding sheet (a sacrificial substrate), 2) a metalfoil already on a thermal debonding sheet (a sacrificial substrate), or3) a metal foil already on a plastic laminate. The contemplated types oflaser ablate the outer edges of the intended circuitry pattern as themetal foil passes reel-to-reel under a laser scanner within thereel-to-reel machine.

There are at least two contemplated ways of laser ablation: 1) ablatinga certain depth using one type of laser followed by another type oflaser to cut a further depth, and 2) ablating through the entirethickness of the metal foil using one laser, following by another laserto refine the ablated edges.

Contemplated laser types include a green laser to ablate a metal patternon the fly, which can ablate the metal foil without damaging anysubstrate underneath the metal foil, such as the plastic laminate. Greenlaser has a high absorption for and can enable at least copper,aluminum, and nickel ablation. It can ablate metal foil moreefficiently. A high-power green laser is particularly contemplated toablate most depth of the metal foil at first in one pass or more thanone pass. 1 um fiber lasers can also be used for this first passspecifically for aluminum. Then a UV laser, more precise green laser, orultrafast lasers (pico, femtosecond, etc.) can be used to ablate theremaining thickness of the metal foil without damaging the underlyingsubstrate. One reason for this is so that the underlying substrate(e.g., UV debonding sheet, thermal debonding sheet) may be recycled andreused in the future. More importantly, carbon contamination will notoccur as much.

There are various ways to remove the negative material resulting fromthe last ablation, depending on various factors. In the contemplatedsituation where the metal foil started out on a UV debonding sheet, itis contemplated that at some point during the fabrication process (e.g.,before or after the laser ablation process), a top UV laminate orthermoset laminate coverlay can be applied on top of the metal foil.Subsequently, UV laser light can be irradiated onto the UV debondingsheet from underneath to precisely just the area of the circuitrypattern, thereby debonding the portion of the UV debonding sheet fromthe circuitry pattern of the metal foil. In some embodiments, the UVlaser irradiates an area of the UV debonding sheet that entirely orsubstantially corresponds to the area of the circuitry pattern.

Further downstream the reel-to-reel conveyor system, the UV debondingsheet can be peeled away from the metal foil, effectively removing thenegative material (which is adhered to the UV debonding sheet) from themetal foil.

In the situation where the fabrication process started out with a metalfoil already on a thermal debonding sheet, the contemplated process toremove the negative material can be similar to the above. At some pointduring the fabrication process (e.g., before or after the laser ablationprocess), a top thermoset laminate coverlay can be applied on top of themetal foil. Subsequently, an IR laser can be irradiated onto the thermaldebonding sheet from underneath to precisely just the area of thedebonding sheet below the circuitry pattern, thereby debonding aspecific portion of thermal debonding sheet from the circuitry patternof the metal foil. In some embodiments, the IR laser irradiates an areaof the thermal debonding sheet that entirely or substantiallycorresponds to the area of the circuitry pattern.

In another embodiment, the thermoset laminate coverlay and IR laser maybe replaced by a UV laminate and a UV laser.

Further downstream the reel-to-reel conveyor system, the thermaldebonding sheet can be peeled away from the metal foil, effectivelytaking the negative material with it.

After the negative material is removed, the underside of the circuitrypattern may have debonding residue on it. There can be an optional CO2laser scanner to clean any debonding residue on the underside of thecircuitry pattern. The CO2 laser scanner can work in conjunction with anappropriate vision system such as a high-definition camera to detect andlocate the presence of debonding residue.

In the situation where the fabrication process started out with a metalfoil already on a plastic laminate, the laser ablation is contemplatedto be done without carbonizing the bottom plastic laminate. In oneembodiment, the plastic laminate is meant to stay adhered to thecircuitry pattern as part of the intermediary product or the endproduct. Also, in some embodiments the negative material can stayadhered to the plastic laminate as part of the intermediary product orthe end product. Because the circuitry pattern can be adequately andprecisely ablated and electronically separated from the negativematerial, the remaining negative material is not expected to interferewith the normal operation of the end product.

In other embodiments which will be discussed in more details later, thenegative material is to be removed from the circuitry pattern.

As such, another aspect combinable with the general implementation is anovel process of removing the negative material.

The contemplated novel method to remove the negative material, or slugs,can allow for faster processing of thicker metal foils duringfabrication. It also eliminates the need for chemical etching.

An optional step includes using compressed air and air nozzles to blowthe slugs off during certain point in the fabrication process, thedetail of which will be discussed later.

In another further improvement on this process is to apply a top linerthat is die cut and has a much stronger adhesive than the bottom lineradhered to the metal foil. The bottom liner can have an adhesivestrength that is sufficiently strong enough so that it can remove thewaste slugs with a higher yield, whether or not compressed air isapplied to blow off the slugs. This process locates the cutouts over thewaste regions.

In another aspect combinable with the general implementation, a novelsintering process to replace or supplement the dip or electroplating ofpads is disclosed.

Typically a component is connected to a flexible printed circuit via thepads on a flexible printed circuit. Some metals, such as aluminum,however, cannot be easily soldered. While plated aluminum is currentlyavailable in the industry, plated aluminum is costly andcost-prohibitive. Therefore, the adaption of using aluminum as a metalfoil in flexible printed circuits has been slow.

The herein disclosed novel sintering process can efficiently andcost-effectively prepare pads on various different types of metal foilon the fly. It should be noted that the sintering process can take placeeither before or after circuitry patterns have been formed. The processgenerally includes using a paste (e.g., tin paste, nickel paste) thathas metal particle fillers. In one way, the paste can be silkscreeneddirectly onto the intended spots of pads on the metal foil. In anotherway, the paste can be silkscreened first onto a sacrificial linerplastic followed by transferring the paste reel-to-reel onto theintended spots on the metal foil. An anvil and a press roller can beused to press the paste onto the metal foil. However the paste is placedonto the metal foil, a laser can be used to irradiate the paste andremove the non-metal portion of the paste while also sintering the metalparticles onto the intended spot of the pads on the metal foil,effectively plating the pads.

In another aspect combinable with the general implementation, a novellamination process reel-to-reel on the fly is disclosed.

As is well known in the industry, current FPC lamination processinvolves a two-step process in a sizeable vacuum oven. Here, thecontemplated reel-to-reel lamination process can take place on the flyin the same reel-to-reel machine where other related processes aretaking place. In one embodiment, the novel process can be performedwithout vacuum. In another embodiment, it can be performed within avacuum enclosure on the fly. The enclosure can be disposed within thereel-to-reel machine and is part of the overall continuous reel-to-reelfabrication conveyor system.

Whenever a coverlay is placed on top of metal foil reel-to-reel, it canbe laminated using the contemplated novel lamination process. Oneexample has been briefly mentioned above where an overlay is placed ontoof the metal foil before the negative material is removed.

The novel lamination process can include placing a UV coverlay on oneside of the metal foil and subsequently passing the UV coverlay througha UV lamp within a vacuum enclosure to cure the adhesive.

In another contemplated example, the novel lamination process caninclude placing a thermo coverlay on a surface of the metal foil. Thethermo coverlay layered on the surface of the metal foil can then passedthrough a heat roller. The heat from the heat roller reflows thethermoplastic and bonds to the metal foil. Alternatively or optionally,a laser light or other known heat lamps can be used to apply heat to thethermo coverlay. These curing processes can optionally be performed in avacuum enclosure, which will be discussed in more details below.

In another aspect combinable with the general implementation, a novellaser welding process reel-to-reel to layer up flexible printed circuitsto create a multi-layer flexible printed circuit is disclosed.

In prior art multi-layer flexible printed circuits, two or more metallayers can be joined together by creating a VIA. The contemplatedwelding methods offer an alternative method of joining layers ofcircuitry patterns.

In some embodiments, a fiber laser can be used to weld two metal foilstogether into a multi-layer format. Contemplated metal types caninclude, but not limited to, stainless steel, nickel, aluminum, andcopper. In particular, a wobble conduction weld technique can be used.

In one example, a rotary die with protruding features that makesembossing features on metal foil 201 is provided to press specific spotsof the two or more layers of metal foils together with sufficientpressure to deform the metal foils. It effectively makes adjacent layersof circuitry pattern physically touch or become closer to each other.Then fiber laser is irradiated to those specific spots to weld thosespots together.

Optionally, before embossing the metal foils, a window can be createdthrough whatever coverlay or substrate that may be in the way of laserwelding so as to expose the intended locations for embossing and/orwelding. This can improve the effectiveness of the embossing, therebyensuring a successful welding process. Any known window-making processescan be implemented. Alternatively, a coverlay with pre-made windows areadhered to the metal foil, eliminated the extra step of creatingwindows.

In another contemplated example, an extremely thin layer of PSA(pressure sensitive adhesive) can be applied between the two layers ofmetal foil. The contemplated adhesive thickness is thinner than 10% ofthe thickness of the top metal foil. The laser can irradiate theintended weld spots to displace the adhesive locally and allow the twometal layers to weld together. In one contemplated example, severalhundred watts CW fiber laser with galvanometer is implemented using awobble weld technique.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular implementations of particularembodiments.

The details of one or more implementations of the subject matterdescribed in this disclosure are set forth in the accompanying drawingsand the description below. Other features, aspects, and advantages ofthe subject matter will become apparent from the description, thedrawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

It should be noted that the drawing figures may be in simplified formand might not be to precise scale. The thickness of certain sheetmaterial in the drawing figures may be exaggerated for ease ofillustration. In reference to the disclosure herein, for purposes ofconvenience and clarity only, directional terms such as top, bottom,left, right, up, down, over, above, below, beneath, rear, front, distal,and proximal are used with respect to the accompanying drawings. Suchdirectional terms should not be construed to limit the scope of theembodiment in any manner.

FIG. 1 illustrates one exemplar reel-to-reel machine workflow layout.

FIG. 2 illustrates another embodiment of workflow to produce an endproduct such as a multi-layer or a single layer flexible printedcircuit.

FIG. 3 illustrates another embodiment of workflow using threereel-to-reel machines each feeding an intermediary product, e.g., asingle-layer flexible printed circuit, into a fourth reel-to-reelmachine to produce an end product such as a multi-layer flexible printedcircuit.

FIG. 4 illustrates another embodiment of workflow using two reel-to-reelmachines each feeding an intermediary product, e.g., a single-layerflexible printed circuit, into a third reel-to-reel machine which whileproducing an intermediary product it also produces an end product suchas a multi-layer flexible printed circuit.

FIG. 5 is a simplified exemplar illustration of a laser ablation processand slug-removal process, according one aspect of the disclosure.

FIG. 6 is a simplified exemplar illustration of a laser ablation processdirectly on the metal foil without carbonizing the bottom plasticlaminate, according one aspect of the disclosure.

FIG. 7 is a simplified exemplar illustration of a workflow highlightingthe laser ablation process and the slug-removal process, according oneaspect of the disclosure.

FIG. 8 is a simplified exemplar illustration of a workflow highlightinga laser ablation process using a sacrificial liner on the bottom and acoverlay on top, wherein the coverlay has selected areas of its adhesivelayer removed by a laser prior to applying the coverlay onto the metalfoil, according one aspect of the disclosure.

FIG. 9 shows a metal foil after laser ablation, where the outer edges ofa circuitry pattern has been ablated, the negatives have been ablatedinto more manageable pieces, and tie bars have been created, accordingto one aspect of the disclosure.

FIG. 10 is a simplified exemplar illustration of a workflow highlightingthe placement of sintering paste by a printer followed by a lasersintering process, according one aspect of the disclosure.

FIG. 11 is a simplified exemplar illustration of a workflow highlightingthe placement of sintering paste by a sacrificial liner followed by alaser sintering process, according one aspect of the disclosure.

FIG. 12 is a simplified exemplar illustration of a workflow highlightingthe placement of a UV coverlay followed by exposure to a UV source,according one aspect of the disclosure.

FIG. 13 is a simplified exemplar illustration of a workflow highlightingthe placement of a thermoset coverlay followed by exposure to a heatroller, according one aspect of the disclosure.

FIG. 14 is a simplified exemplar illustration of a workflow highlightinga lamination process using a vacuum source, followed by exposure to a UVsource, according one aspect of the disclosure.

FIG. 15 is a simplified exemplar illustration of a workflow highlightinga lamination process using a vacuum source, followed by exposure to aheat source, according one aspect of the disclosure.

FIG. 16 is yet another simplified exemplar illustration of a workflowhighlighting a lamination process using a vacuum source and a UV source,according one aspect of the disclosure.

FIG. 17 is still another simplified exemplar illustration of a workflowhighlighting a lamination process using a vacuum source and a heatsource, according one aspect of the disclosure.

FIG. 18 is a simplified cross-sectional side view illustrating amulti-layer flexible printed circuit prior to a laser welding process,according one aspect of the disclosure.

FIG. 19 is a simplified cross-sectional side view illustrating amulti-layer flexible printed circuit after an embossing step, accordingone aspect of the disclosure.

FIG. 20 is a simplified cross-sectional side view illustratingproportions between the various layers, according one aspect of thedisclosure.

FIG. 21 is a simplified illustration of a workflow highlighting anembossing process and a welding process, according one aspect of thedisclosure.

FIG. 22 is a simplified illustration of a workflow highlighting a laserwelding process without embossing, according one aspect of thedisclosure.

FIG. 23 is a simplified cross-sectional side view illustrating two metalfoils prior to laser welding, according one aspect of the disclosure.

FIG. 24 is a simplified cross-sectional side view illustrating two metalfoils after laser welding, according one aspect of the disclosure.

FIG. 25 is another simplified cross-sectional side view illustrating twometal foils prior to placement of a sintering paste, according oneaspect of the disclosure.

FIG. 26 is another simplified cross-sectional side view illustrating twometal foils after placement of a sintering paste, according one aspectof the disclosure.

FIG. 27 is another simplified cross-sectional side view illustrating twometal foils after the sintering paste has been irradiated by laser,according one aspect of the disclosure.

FIG. 28 is a simplified illustration of a reel-to-reel process of thesequence of steps in FIGS. 25-27, according one aspect of thedisclosure.

The following call-out list of elements in the drawing can be a usefulguide when referencing the elements of the drawing figures:

-   -   1 Reel-to-Reel Machine    -   2 Beginning material    -   3 Feeder    -   4 Reel    -   5 Intermediary Product    -   6 Reel-to-Reel Machine    -   7 Reel-to-Reel Machine    -   8 Housing    -   9 End product    -   11 Driving Motor    -   15 Microprocessor    -   200 Laser Ablation Module    -   201 Metal Foil    -   202 First Surface    -   203 Second Surface    -   204 Sacrificial Liner    -   205 Laser Scanner    -   206 Plastic Laminate    -   207 Vacuum Enclosure for Ablation    -   208 Z Height Setter    -   221 Circuitry pattern    -   222 Outer Edge    -   223 Negative Material/Slug    -   225 Tie Bar    -   226 Residue    -   231 Patterning Step    -   232 Rough Ablating    -   233 Fine Ablating    -   234 Cutting a First Depth    -   235 Cutting a Second Depth    -   300 Slug-Removal Module    -   301 UV Laminate/Thermoset Laminate    -   302 UV or Thermoset Coverlay    -   303 Reel    -   305 Laser Scanner    -   306 Tracking Scanner    -   307 UV Laser Scanner    -   308 Vision System    -   309 Laser Scanner    -   310 Laser Scanner    -   311 High-Pressure Blower    -   312 Slug-Collecting Tray    -   313 Vision System    -   314 Sacrificial Liner    -   315 Vacuum Enclosure for Ablation    -   316 Plastic Coverlay    -   317 UV Laser Scanner    -   331 Visualizing and Tracking Step    -   332 Placing Coverlay on Top    -   333 Data received by microprocessor    -   334 Debonding Step    -   400 Sintering Module    -   401 Paste    -   402 Laser Scanner    -   404 Pad location    -   405 Vision System    -   406 Sacrificial Liner    -   408 Vision System    -   409 Sintered spots    -   410 Printer    -   500 Lamination Module    -   501 Nip Roller    -   502 Anvil    -   503 UV Lamp    -   508 Heated Nip Roller    -   509 Anvil    -   510 Vacuum Enclosure    -   512 Sealed entrance    -   513 Sealed Egress    -   515 Suction Nozzle    -   518 Suction Source    -   519 Heat Source    -   550 Laser Scanner    -   552 Vision System    -   600 Welding Module    -   601 First Metal Foil    -   602 Second Metal Foil    -   603 Top Dielectric Layer    -   604 Middle Dielectric Layer    -   605 Window    -   606 Molten metal    -   607 Hollow space    -   608 Sintered Paste    -   609 Weld Spot    -   609 Nip Roller    -   610 Debossing Die    -   611 Anvil    -   612 Deformation    -   620 Laser Scanner    -   641 Vision System    -   642 Laser Scanner    -   661 Rotary Die Cutter    -   662 Anvil    -   663 Sacrificial Liner    -   671 Rotary Die Cutter    -   672 Anvil    -   673 Sacrificial Liner    -   681 Reel    -   682 Reel    -   683 Reel    -   684 Reel    -   685 Reel    -   686 Reel    -   690 Z Height Setter    -   691 Z Height Scanner    -   700 Depaneling Module    -   701 Rotary Die Cutter    -   702 CO2 Laser Cutter

DETAILED DESCRIPTION OF THE EMBODIMENTS

The different aspects of the various embodiments can now be betterunderstood by turning to the following detailed description of theembodiments, which are presented as illustrated examples of theembodiments as defined in the claims. It is expressly understood thatthe embodiments as defined by the claims may be broader than theillustrated embodiments described below.

The inventor has discovered a novel method of fabricating a flexibleprinted circuit (FPC) that either entirely or partially eliminates theuse of a gantry. As will be described in more details below, some of theprocesses can optionally include the use of a gantry. Other embodimentsmay supplement any of the herein disclosed reel-to-reel fabricationprocesses with the use of a gantry at some point of the fabricationprocess. For the most part, many of the below disclosed embodimentsrelate to a novel reel-to-reel fabrication process of a flexible printedcircuit (FPC). The end product may be a single-layer flexible printedcircuit or a multi-layer flexible printed circuit.

In many of the embodiment to be discussed in detail, the novelreel-to-reel fabrication process relates to a process whereby one ormore continuous sheet of material are fed into a reel-to-reel machine.In some embodiments, more than one reel-to-reel machine may be necessaryto each separately fabricate a layer of flexible printed circuit, andthen each individually produced layer of flexible printed circuit arecombined using a yet another novel process to result in a multi-layerflexible printed circuit. To that end, this disclosure contains 1) anovel standalone reel-to-reel machine having various modules to producea single-layer or a multi-layer flexible printed circuit, 2) a novelsystem of flexible printed circuit fabrication using multiplereel-to-reel machines to produce a multi-layer flexible printed circuit,and 3) individually novel processes/modules within a single reel-to-reelmachine.

The concept of novel reel-to-reel fabrication in FPC manufacturing willbe discussed first, followed by discussions on each of the individuallynovel processes/modules. It will, nevertheless, be understood that nolimitation of the scope of the disclosure is thereby intended by thespecific sequences these modules are presented below. For example,although the “laser ablation” process may be discussed prior to the“sintering process,” the disclosure is not to be limited to having laserablation occurring prior to sintering.

Also, it should be understood that in some embodiment, any one or moreof the discussed processes/modules may be replaced with a suitableprocess known in the industry. In other words, in some embodiments, anyof the contemplated modules below does not necessarily require that anyother one or all of the contemplated modules to be necessarily present.For example, while the “laser ablation” process may be discussed in someembodiments as part of a series of other processes (e.g., lamination,sintering) to manufacture a certain intermediary product or end-product,the novelty of the lamination process shall not require the disclosedlaser ablation process. The lamination process can stand on its ownwithout requiring the laser ablation process. Also, any of theseindividual processes/modules may be replaced by a prior art method. Forexample, the herein disclosed novel sintering and lamination process cantake place even if the circuitry pattern is formed by a typical chemicaletching process. Yet in some other embodiments, any of the contemplatedmodules discussed herein does necessarily require that any other one orall of the contemplated modules to be necessarily present.

Therefore, certain features, processes, method steps, and modules thatare described in this specification in the context of separateimplementations of multiple processes/modules can also be implemented ina different arrangement and sequences of one or more processes/modules.Conversely, various features that are described in the context of asingle implementation can also be implemented in multipleimplementations separately or in any suitable subcombination.

Likewise, one or more features from a combination can in some cases beexcised from the combination, and the claimed combination may bedirected to a subcombination or variation of a subcombination

As such, any alterations, permutations of process sequence, and furthermodifications of the described or illustrated embodiments and anyfurther applications of the principles of the disclosure as illustratedtherein are contemplated as would normally occur to one skilled in theart to which the disclosure relates.

As used herein, the term “continuous” in conjunction with a metal foil,coverlay, laminate material, substrate material refers to a state offeeding said sheet material into the reel-to-reel machine from one reelto another reel. In one embodiment, it can mean a very long roll ofmaterial that continues to feed into the machine such that when theleading end has exited the machine, the trailing end has yet to enterthe machine. In another embodiment, it can mean a sheet materialsufficient long enough for its leading end to make one turn at a reelwhile its trailing end is still passing over another reel. In yetanother embodiment, it can mean a sheet material sufficiently long tohave more than one intended flexible printed circuit arranged on thesame sheet in a lengthwise, consecutive fashion.

Reel-to-Reel FPC Fabrication Device and Method

FIG. 1 generally depicts the basic architecture of one embodiment of areel-to-reel machine 1, wherein a beginning material 2 is fed into thefeeder 3. The feeder has the associated accessories such as motor androtors to grab the beginning material 2 and feeding it into thereel-to-reel machine. As is known in typical reel-to-reel machines,there are various reels 4 disposed throughout the reel-to-reel machine1, feeding, transporting, directing, pressing the various sheetmaterials.

The reel-to-reel machine 1 can have various components, or modules toperform various tasks in the reel-to-reel conveyor system. FIG. 2provides a general overview of one contemplated workflow, according toone aspect of the reel-to-reel FPC fabrication method. Here, thisparticular workflow requires a laser ablation module 200, a slug-removalmodule 300, a sintering module 400, and at least one lamination module500 dispersed within any of the other modules. A single-layer flexibleprinted circuit is produced (i.e., end product 9) after a depanelingmodule 700 which may include a rotary die cutter (not shown) or a CO2laser cutter (not shown).

It should be noted that this is only one example of workflow having anexemplar sequence of modules. Many other and different sequences ofmodules are possible and one of ordinary skill in the art wouldimmediately understand and recognize other possible ways to arrangethese modules. For example, the ablation module 200 does not necessarilyhave to take place prior to the sintering module 400, and one skilled inthe art would understand from this disclosure that slug-removal module300 may have to take place after the laser ablation module 200.

Also, various components of the contemplated reel-to-reel machine 1 areherein artificially categorized into “modules.” While certain componentmay be built into a unitary module, certain components may be dispersedthroughout the overall reel-to-reel conveyor system. For example, therecan be various places in the reel-to-reel conveyor system wherelamination takes place. There can be one or more lamination steps insome of the above-mentioned modules. Therefore, as an example,lamination steps are not necessary performed only at a specific locationby a specific modular unit of lamination machine. The same applies withother above-mentioned modules. For example, while one workflow diagrammay show a single sintering module, some implementations may have thevarious required steps of sintering taking place at various locationsupstream and downstream in the overall reel-to-reel conveyor system. Forexample, the first part and the second part of the sintering process maybe separated by the laser ablation process. One of ordinary skill theart would immediately recognize from this disclosure that the disclosedcomponents are versatile and can be re-arranged to suit specific designneeds.

FIG. 3 provides another contemplated workflow, according to one aspectof the reel-to-reel FPC fabrication method. Here, this particularworkflow requires four separate reel-to-reel machines. Three similarreel-to-reel machines 1 each has a laser ablation module 200, aslug-removal module 300, a sintering module 400, and a lamination module500. These three reel-to-reel machines 1 each can produce a single-layerflexible printed circuit (i.e., an intermediary product 5), all of whichcan then be fed into a fourth reel-to-reel machine 6 to be combined intoa multi-layer flexible printed circuit (i.e., end product 9). The fourthreel-to-reel machine 6 is unlike the other reel-to-reel machines in thatits function is to receive intermediary products 5 for furtherprocessing into a multi-layer flexible circuit (i.e., the end product 9.In particular, the third reel-to-reel machine has a welding module 600and a depaneling module 700.

FIG. 4 provides yet another contemplated workflow, according to oneaspect of the reel-to-reel FPC fabrication method. Here, reel-to-reelmachine 7 can have a laser ablation module 200, a slug-removal module300, a sintering module 400, a lamination module 500, welding module,and depaneling module. Reel-to-reel machine 7 can make the intermediaryproduct 5, and can combine it with intermediary products 5 received fromreel-to-reel machines 1. Reel-to-reel machine then produces end product9, which is a multi-layer flexible printed circuit.

Detailed parts disposed within any of these reel-to-reel machines 1, 6and 7 will be discussed in the following sections. One of ordinary skillin the art would immediately recognize that the implementation of manyof the herein disclosed embodiments may require basic known reel-to-reelequipment (e.g., housing, microprocessor, control panel, sensors,motors, reels and anvils, measurement and adjustment means). Descriptionand discussion of these commonly known and necessary parts of areel-to-reel operation are herein omitted because they are well withinthe ordinary skill of reel-to-reel technology. Also, some components orsteps commonly known in prior art FPC fabrication are also hereinomitted because they are well within the ordinary skill of FPC or PCBfabrication. For example, removing dust or preventing dusts fromaccumulating on the circuitry pattern.

In one embodiment, the contemplated reel-to-reel machine is capable offabricating a printed flexible circuit on the fly. There can be ahousing 8 (FIG. 4), a driving motor (FIG. 4), a nip roller 501 (FIG.12), and an anvil 502 (FIG. 12) disposed within the housing. There canbe a microprocessor 15 (FIG. 4) connected to the machine by wire orwirelessly. The microprocessor can be part of the machine or an add-on.There is a plurality of reels within the housing that defines a conveyorroute for the passage of a metal foil reel-to-reel. Along the conveyorroute other sheet materials can be introduced and added to the metalfoil, as will be discussed in more details later.

Up and down stream of the conveyor route in a reel-to-reel direction,the conveyor route generally has a top side and a bottom side. The topside and the bottom side are parallel to each other and many of thecomponents to be discussed below can be positioned on either side. Itshould be noted that while this disclosure may initially describe acomponent being on either a top side or a bottom side, one skilled inthe reel-to-reel technology would understand that a reverse arrangementcan be possible. In some embodiments, when two components are describedas being on one particular side of the conveyor route, one skilled inthe reel-to-reel technology would understand that the two components mayalso be arranged on opposite sides of each other in some scenariosdepending on the design of the workflow.

Laser Ablation Device and Method

Contemplated method of creating a predetermined circuitry pattern on ametal foil 201 reel-to-reel can include feeding a continuous sheet ofmetal foil 201 into the reel-to-reel machine. Contemplated metal foil201 includes at least one of aluminum, Ni-plated aluminum, Ni-platedcopper, nickel, stainless steel, and copper.

As shown in FIGS. 5-6, the sheet of metal foil 201 has a top side 202and the bottom side 203. In FIGS. 5-6, the sheet of metal foil 201 is ontop of a layer of substrate. This substrate, as will be described below,can be a sacrificial liner 204 such a UV debonding sheet (FIG. 5) or athermal debonding sheet (also FIG. 5). This substrate can also be aplastic laminate 206 (FIG. 6).

As used herein, the term “cut” or “cutting” in conjunction laserablating the metal foil 201 refers to the commonly known photoablationprocess of removing certain portions of the metal foil 201 byirradiating it with a laser beam. It does not refer any mechanicalremoval process or chemical removal process.

Referring now to FIG. 5, there can be a sacrificial liner 204 attachedto the bottom side 203 of the metal foil 201. This sacrificial liner 204as illustrated in FIG. 5 can either be a UV debonding sheet or a thermaldebonding sheet. Any other known sacrificial sheet material suitable forthe purposes described below can also be used.

At the laser ablation module 200, starting with the combination of metalfoil 201 and the sacrificial liner 204, there is a laser scanner 205within the reel-to-reel machine 1 to perform patterning of thepredetermined circuitry pattern 221.

The laser scanner 205 can use a fiber laser to ablate the edge 222 of acircuitry pattern 221 on the fly. Other types of laser are alsocontemplated, including a green laser, UV laser, and 1 um pico secondand femto second lasers. In the example as shown in FIG. 6, a greenlaser can be used to ablate the edge 222 of the circuitry pattern 221foil without damaging the plastic laminate 206 underneath the metal foil201. Also, green laser has a high absorption for and can enable at leastcopper, aluminum, and nickel ablation. A high-power green laser isparticularly contemplated to ablate most depths of the metal foil 201first in one or more passes. Then a UV laser, a more precise greenlaser, a 1 um pico second, or a femto second lasers can be used toablate the remaining thickness of the metal foil 201 without damagingthe underlying plastic laminate 206.

Even in situations where a sacrificial liner 204 such as a thermaldebonding sheet or a UV debonding sheet is used (as shown in FIGS. 5,6), a more precise laser ablation as described above minimizes damage tothe sacrificial liner 204. The sacrificial liner 204 that is minimallydamaged may be recycled and reused, making it an environmentally andeconomically sound solution. In a preferred embodiment, the laserablation is performed without ablating through the sacrificial liner204. Additionally, a more precise laser ablation allows very accuratepattern ablation.

Alternatively, the laser scanner 205 can first rough-ablating throughthe entire thickness of the edge 222 using a green laser or 1 um fiberlaser, following by a UV laser, or a more precise green laser, a 1 umpico second, or a femto second lasers. In operation, the laser scanner205 irradiates a laser beam onto the top side 202 of the metal foil 201along the outer edge 222 of the predetermined circuitry pattern 221 (seeFIG. 9). One or more than one passes of the laser is contemplated toeventually and thoroughly cut through the thickness of the metal foil(cutting through the outer edge 222). In one embodiment, the metal foil201 stops traveling through the reel-to-reel conveyor system duringlaser ablation. In another embodiment, the metal foil 201 continues totravel through the reel-to-reel conveyor system during laser ablation.

In FIG. 9, the outer edge 222 of the circuitry pattern 221 has been cutentirely through, physically separating the circuitry pattern 221 fromthe negative material 223. As will be discussed in a later section, thenegative material 223 can be subsequently removed in various novelmethods. Here, one aspect of the inventive subject matter includes usingthe laser scanner 205 to ablate relatively larger or longer pieces ofnegative material 223 into smaller portions (as illustrated by dashedlines in FIG. 9). This can facilitate subsequent slug-removal steps.

During laser ablation, a portion of the ablated metal foil 201 isconverted to plasma. There can be provided certain suction nozzles orexhaust mechanism to suck the plasma out of the reel-to-reel machine 1.

In some embodiments, the contemplated laser ablation module 200 can beenclosed in a vacuum enclosure 207 in part or in whole. The laserablation module 200 is also contemplated to use a Z height setter 208(FIG. 7) to assist in making proper alignment and adjustment. This canapply to any other laser scanner discussed in this disclosure. The Zheight scanner can be located at the specific Z height for focuslocation of laser. The laser head or Z height scanner bed, however,could actively move if the Z height is variable or if even bettertolerance can be achieved with a vision system.

The vacuum enclosure 207 and another other vacuum enclosure discussed inthe disclosure can be a true vacuum condition where the enclosure isdevoid of air. In other embodiments, this can be a near-vacuum conditionwhere negative pressure is applied when necessary, but the force of thesuction may not be enough to create a true vacuum condition. In yetother embodiments, such as what's shown in FIGS. 14 and 15, it can be anenclosure with movable and/or flexible body such that a source ofsuction 518 can assert sufficient negative pressure to cause the movableand/or flexible body to clamp, or squeeze, onto whatever material thatis within the enclosure. If a clamping or flexible membrane is used tocreate even more suction then the surface energy of the membrane must besufficiently low such that the sheet material can still pass through theclamping or flexible membrane.

In another aspect of the embodiments, the laser scanner 205 canpurposely create tie bars 225 (see FIG. 9) all of which connect some orall parts of the circuitry pattern 221 with each other. Tie bars 225 canbe created by intentionally leaving certain portions of the negativematerial as connecting bars 225 to connect all circuitry patterns 201together as one single integral unit. Many such tie bars 225 can becreated, connecting not only parts of a single circuitry pattern 201 toitself, but also physically connecting adjacent circuitry patterns 201to one another. The laser scanner 205 can thin out the two terminal endsof each tie bar 225 thereby creating small neck regions. The small neckregions can allow easier subsequent removal of these tie bars 225.Again, the contemplated tie bars 225 can offer structural support to thecircuitry pattern 221 as the circuitry pattern 221 goes furtherdownstream into the reel-to-reel conveyor system. For example, tie bars225 can be created for the workflow shown in FIG. 7, the detail of whichwill be discussed later. Because tension may cause the web of metal foilto wrinkle, one contemplated method to prevent wrinkling is to have tiebars oriented in the direction of travel and the direction perpendicularto it. Tie bars may also be in crisscrossed configuration, or a webconfiguration to counteract tension in multiple directions. Orientingonly in the direction of travel would require a sufficiently wide enoughtie bar to counter tension without wrinkling.

If the ablated circuitry pattern 221 were supported from its bottom side203 with a plastic laminate 206 (as in FIG. 6), the circuitry pattern221 may or may not need tie bars 225 as a structural support. Theplastic laminate 206 can sufficiently keep the integrity of thecircuitry pattern 221, unless the laser scanner 205 had defectively cutthrough the underlying plastic laminate 206 at some places.

Tie bars 225 can be subsequently removed at a later stage (to bediscussed below in Slug-Removal Device and Method) via another laserscanner (310 in FIG. 7) downstream from here.

In some embodiments, a coverlay 302 can be placed onto top side 202 ofthe metal foil 201 subsequent to the laser ablation process (see FIGS. 5and 6).

Slug-Removal Device and Method

As mentioned earlier, some embodiments of the disclosed FPC fabricationprocess require the removal of the slugs 223. The slug-removal deviceand method described herein is to take place subsequent to the laserablation module 200. It may or may not come immediately after the laserablation module 200. There may be intervening steps or modules takingplace prior to slug removal. In some embodiments, the laser ablationthat is to take place prior to slug-removal may be replaced by othermeans of creating a circuitry pattern, such as by traditional chemicaletching. For example, an outline of the circuitry pattern may be firstchemically etched away outside of the reel-to-reel machine, before thecircuitry pattern is fed into the reel-to-reel machine for the hereindiscussed slug-removal process.

As used herein, the term “negative material” or “slug” in conjunctionwith removing the unwanted portion of the metal foil refers to portionsof the metal foil 201 that are not intended to remain as part of the endproduct 9. If a slug is referred to as a loose slug in thespecification, it does not specifically describe or limit itself to howloosely or not loosely such negative material is initially attached tothe circuitry pattern 221 before removal.

As used herein, the noun “laminate” and “coverlay” in conjunction with asheet material being adhered to the metal foil 201 are synonymous witheach other in many of the embodiments mentioned herein. For example, aUV laminate 302 is sometimes referred to as a UV coverlay 302 in thisdisclosure. They both refer to the same thing. In some otherembodiments, the coverlay can include other sheet material nottraditionally considered to be a laminate sheet. Both “laminate” and“coverlay” refer to a two-part sheet form material comprised of asupport film layer (e.g., polyimide) and a layer of adhesive (e.g.,epoxy or acrylic based flexible adhesive, such as pressure sensitiveadhesive, PSA), The thermoset materials and UV laminate can and do havean initial tact (like PSA) so it can be adhered to the metal foil priorto a thermal or UV lamination.

As used herein, the term “UV laminate” refers to a plastic laminatehaving a UV adhesive disperse on one side. The UV adhesive can beactivated and cured by exposing it to UV radiation. A UV laminate can becreated by taking a high viscosity gel UV adhesive and spread it over aplastic laminate like PET or PI (polyimide) using currently knownprocesses (e.g., curtain coating, slot die coating).

Referring back to FIG. 5, a sacrificial liner 204 may be used to removethe slugs 223. Here, a UV debonding sheet 204 or a thermal debondingsheet 204 can be adhered to the bottom side 203 of the metal foil 201.This sacrificial liner 204 maybe pre-adhered to the metal foil 201 priorto feeding the metal foil 201 into the reel-to-reel machine 1, or it maybe applied reel-to-reel onto the metal foil 201 within the reel-to-reelmachine 1. FIG. 7 shows one such example.

In FIG. 5, at some point after the laser ablation process 200, a top UVlaminate or thermoset laminate 302 coverlay can be applied on top of theablated metal foil 201 reel-to-reel. This coverlay 302 can keep thestructural integrity of the ablated circuitry pattern 221 intact duringthe subsequent slug-removal process. The timing and procedure to curethis top coverlay are discussed in the “lamination” section of thisdisclosure.

At some point downstream from where the top coverlay 302 was applied, aUV laser scanner 307 can be provided to irradiate from underneath thesacrificial liner 204. As shown in FIG. 5, UV laser scanner 307selectively irradiates specific areas of the sacrificial liner wheredebonding from the metal foil 201 is desired. For example, it canirradiate all circuitry patterns 221 (not the edge 222) thereby makingonly the unwanted negative material 223 to remain bonded to thesacrificial liner 204. The support film layer of the UV debonding sheetis transparent to UV to ensure the UV radiation can reach the adhesive.

UV laser scanner 307 can use UV LED with optics to provide aconcentrated beam of light. It could also be a solid state UV lasersource. Another choice can be a high power UV laser light in the rangeof 400 nm to 450 nm. While UV spectrum is from 255 nm to 405 nm,application for the UV adhesives are between 365 nm and 420 nm.

The spot size of the laser beam for debonding can be adjusted to belarger to match the speed of the metal ablation laser. Other adjustmentcan also be made such as adding additional laser scanner to perform thedebonding. The focus of the laser beam can be unfocused to control thepower flux of the light. This is not a linear, but a sensor feedbackwith z height can allow for some control of this power flux.

In situations where a thermal debonding sheet 204 is used in place of UVdebonding sheet 204, the process is similar. An IR laser scanner 307 canselectively apply heat to specific areas of the thermal debonding sheetwhere debonding from the metal foil 201 is desired.

Selective irradiation by the UV laser scanner 307 can be done preciselythrough the help of a tracking scanner 306. Tracking scanner 306 can bea vision system including a high-definition camera. It can includeinline AOI (automated optical inspection) hardware. It can be disposedon the same side as the laser scanner 205 to visualize and track theablated circuitry pattern 221 and provide necessary data to amicroprocessor. The microprocessor can make calculations and send datasignal to the UV laser scanner 307 with respect to exactly where toirradiate.

Besides selectively irradiating the negatives by a beam of UV laser orIR laser, one further contemplated method includes using a UV oven or aUV source/heat source that indiscriminately irradiate the entire surfaceof the debonding sheet, whether it's a UV debonding sheet or a thermosetdebonding sheet. Prior to indiscriminately irradiate the entire surfaceof the UV debonding sheet, an opaque pattern correlating with thecircuitry pattern 221 (or whatever areas that should not be debonded)can be laminated or printed on the surface of the UV debonding sheet.This opaque pattern allows irradiation to only selected areas that needto be debonded. In the case of a thermal debonding sheet, a pattern ofheat reflective material can be printed or laminated on the surface ofthe thermal debonding sheet, thereby allowing heat to be applied only toselected areas that need to be debonded.

The sacrificial liner 204 is next peeled away from the circuitry pattern221 when the sacrificial liner 204 changes direction of travel aroundreel 303. It should be noted that this peeling away process may takeplace immediately after, or much later after irradiation by the UV laserscanner 207 or IR laser scanner 307. In some instances, peeling awayshould take place much later so that sufficient time is given fordebonding sheet deactivation. Negative material 223 remains adhered tothe sacrificial liner 204 as the sacrificial liner moves downward awayfrom the circuitry pattern 221.

Any debonding residue left remaining on the bottom side 203 of thecircuitry pattern 221 can be detected by yet another vision system 308using known image detection methods and provide feedback to themicroprocessor. The microprocessor in turn sends command signals to yetanother laser scanner 309 disposed on the underside of the circuitrypattern 221. The laser scanner then irradiates a laser beam to removethe debonding residue from the circuitry pattern 221.

In FIG. 7, the unablated metal foil 201 has a sacrificial liner 204adhered reel-to-reel to its bottom surface 203. Next, the two-layersheet material is transferred reel-to-reel into an optional vacuumenclosure 207 for laser ablation by laser scanner 205. Laser scanner 205can be disposed on the topside of the metal foil 201.

The optional vacuum enclosure 207 can ensure an optimal adhesion betweenthe two layers. As the laser scanner 205 ablates the edge 222 of thecircuitry pattern 221, it can optionally create tie bars 225 asdiscussed above. In one particular embodiment, the ablation of the metalfoil 201 by laser scanner 205 can result in a metal “web” having thecircuitry pattern 221, the tie bars 225, and a perimeter to keep the webstructurally sound. At some point downstream the reel-to-reel workflow,the perimeter can be removed from the circuitry pattern using any of theherein disclosed slug-removal methods. For example, the perimeter can bemoved at the very end of the reel-to-reel workflow when the intermediateproduct 5 or the end product 9 is being depaneled. The perimeter canhave various sizes and shapes to provide the needed structural support.In one embodiment, the perimeter maintains the outer edges of theoriginal metal foil 201 such that the web would be a continuous websheet have a straight leading edge and two parallel straight side edges.In another embodiment, the perimeter can be wider than a width of asingle circuitry pattern 221. In yet another embodiment, the perimeteris similar to the picture frame. In still yet another embodiment, theperimeter can be two parallel bands along the left and right side of themetal foil 201.

The laser scanner 205 ablates through the depth of the edges 222. In oneembodiment, the laser scanner 205 does not ablate into the optionalsacrificial liner 204. If the laser scanner 205 does not ablate throughthe sacrificial liner 204, the sacrificial liner 204 can be usedtogether with a UV laser scanner 307 (as in FIG. 5) to remove the slugs223 as described previously. Take FIG. 7 as an example, one may insert aUV laser scanner 307 (of FIG. 5) downstream from laser scanner 205 andupstream from the first labeled reel 303. This would allow debonding andpeeling off of the slugs 223, followed by a high pressure blower 311 toblow off any remaining slugs 223.

FIG. 7, however, illustrates a less-preferred embodiment where there isno UV laser scanner 307 to debond sacrificial liner 204 immediatelydownstream from laser scanner 205. Here, the laser scanner 205 canthoroughly ablate through edge 202 and does not ablate the sacrificialliner 204. After the sacrificial liner is peeled off via reel 303, ahigh pressure blower 311 can indiscriminately blow a high-pressurestream of air onto the top of the web of metal foil 201, which includesthe perimeter, the circuitry pattern 221, tie bars 225, and slugs 223.This stream of air can blow off slugs 223 that were physically separatedfrom the circuitry pattern 221 during the laser ablation process 200. Aslug-collecting tray 312 can be provided underneath to catch any fallingslugs 223. After this process, what's left on the conveyor systemreel-to-reel is a connected web of circuitry patterns 221, perimeter,and tie bars 225.

Further downstream from here is an optional vision system 313 tovisualize the ablated circuitry pattern 221 and associated tie bars 225(and any external tension frames). There can be another optionalsacrificial liner 314 applied reel-to-reel to the bottom surface 203 ofthe circuitry pattern 221. At some point downstream this connected webof circuitry patterns 221 is transferred into another laser ablationmodule where a laser scanner 310 is to separate the tie bars 225 (andany external tension frames) from the circuitry pattern 221. The visionsystem 313 provides data to the microprocessor which in turn sendssignal to the laser scanner 310 on exactly where to make the necessaryablation. This ablation module can optionally be enclosed in a vacuumenclosure 315. The vacuum enclosure 315 can enhance adhesive between thelayers and ensure that the separated tie bars 225 (and any externaltension frames) are adequately adhered to the sacrificial liner 314.

Next, a plastic coverlay 316 can be applied to the top side of thetwo-layer sheet (circuitry pattern 221 and sacrificial liner 314) toprovide structural support to the circuitry pattern 221 which isespecially necessary when the tie bars 225 (and any external tensionframes) is to be removed next. It should be noted that the plasticcoverlay 316 may instead be applied to the top side of the metal foil201 prior to the laser scanner 310 removing the tie bars 225.

Subsequently, a UV laser scanner 317 receives a command signal (based ondata collected by the vision system 313) from the microprocessor toselectively irradiate an area of the sacrificial liner 314 thatresembles the circuitry pattern 221. In this way, the tie bars 225 (andany external tension frames) remain adhered to the sacrificial liner 314while the circuitry pattern 221 is debonded from the sacrificial liner314.

As the sacrificial liner 314 peels away from the moving direction of thecircuitry pattern 221, tie bars 225 (and any external tension frames)are effectively removed from the circuitry pattern 221. Because thissacrificial liner 314 is optional, if the sacrificial liner is not usedhere, the tie bars 225 can just drop off from the circuitry pattern 221.

There can be an optional vision system (not shown) and laser scanner(not shown) similar to 308 and 309 of FIG. 5 to detect and remove anydebonding residual from the bottom surface 203 of the circuitry pattern221.

Another improvement contemplated for any of the above slug-removalprocess is to ablate any slugs 223 into smaller and/or shorter piecesbefore removal. In FIG. 9, long pieces of slugs 223 can be ablated by alaser scanner into shorted pieces, and there is shown on relativelylarger piece of slug 223 that is ablated into five manageable pieces(223A, 223B, 223C, 223D, 223E).

FIG. 8 illustrates one embodiment where a top coverlay 302 can be firstablated by laser scanner 305 to selective remove certain portion of itsadhesive layer. Here, metal foil 201 first has a sacrificial liner 204applied to its underside. Then, the metal foil 201 undergoes ablation bylaser scanner 205 to create a circuitry pattern 221. Downstream fromhere, a vision system 306 can collect visual data of the circuitrypattern 201 and allows a downstream laser scanner 305 to ablate theadhesive layer 302 so that the ablated pattern may match up with thecircuitry pattern 221 on metal foil 201. Adhesive layer 302 may beablated without damaging the support film layer of the coverlay. Inother words, only the adhesive layer is removed, and only an area thatentirely or substantially corresponds to the negative material 223 ofthe metal foil 201 is removed.

The coverlay 302 is then applied unto the top surface 202 of the metalfoil 201. Unablated portion of the adhesive layer on the underside ofthe coverlay 203 is contemplated to correspond entirely or substantiallyto the circuitry pattern 221. When sacrificial liner 204 is peeled awayvia reel 303, it would attempt to take the circuitry pattern 221 and theslugs 223 with it. However, because the adhesive layer on the undersideof the coverlay 203 is contemplated to have stronger peel strength thanthe adhesive of the sacrificial liner 204, only the slugs 223 would beremoved. Note that in this example, the sacrificial liner 204 did notrequire a debonding process. In other embodiments, an optional debondingprocess can be added.

Laser Sintering Device and Method

The following description refers to a novel method of plating designatedpads on an unablated metal foil 201, or on a circuitry pattern 221. Thedesignated pads can be a thru-hole pad or a surface mount pad. The metalfoil 201 can be made of aluminum, tin, nickel, and copper.

Referring now to FIGS. 10 and 11, where a metal foil 201 is beingtransferred reel-to-reel within the reel-to-reel machine 1. The novelsintering device and method involve placing a paste 401 onto designatedspots of the pad locations 404 on the metal foil 201, followed byirradiating the paste 401. The paste 401 can include metal particlefiller in it. When the paste 401 is irradiated by a laser scanner 402,the non-metal component of the paste is removed while the metal particlefiller is sintered onto the pad locations 404.

In FIG. 10, the paste 401 can be directly printed onto the pad locations404 via a depositor disposed within the housing on either the top sideor the bottom side of the conveyor route. This contemplated depositor iscapable of depositing a sintering paste 401 on the fly onto the metalfoil 201. In one embodiment, the depositor is a printer 410 having aprint head. Printer 410 can be a laser printer type or an inkjet printertype of technology. Printer 410 can also be a silkscreen printer. If thecircuitry pattern 221 has been created prior to the sintering module400, then a vision system 408, which may include a high-definitioncamera or other relevant sensors, can be provided to visualize therelative locations of the pad locations 404. This data is collected andprocessed by a microprocessor, which in turn send a command signal tothe printer 410. The command signal directs the printer 410 to place thepaste 401 onto the actual pad locations 404. The microprocessor can alsosend a command signal to a downstream laser scanner 402, directing it toirradiate the actual pad locations 404 which now have paste 401 on them.Laser scanner 402 may implement a fiber laser. As mentioned before,non-metal portion of the paste 401 are then removed by the laser, andthe metal fillers of the paste 401 are directly sintered onto the padlocations 404.

In another embodiment, the metal foil 201 can be unablated prior to thesintering module 200. That is, an unablated sheet of metal foil 201 canbe sintered first in designated pad locations 404, and subsequently uselaser scanner 205 to ablate a circuitry pattern 221 using the sinteredspots 409 as reference points. In this case, vision system 408 would beoptional, and there would be vision system 405 downstream from theprinter 410 to detect actual locations of the paste 401. This data isthen provided to a microprocessor which in turn sends a command signalto the laser scanner 402. The command signal directs the laser scanner402 to irradiate the exact locations of these paste 401. Themicroprocessor may also send command signals to relevant components ofthe laser ablation module 200, such as the laser scanner 205 in FIG. 5so that subsequently the laser scanner 205 would ablate a desiredcircuitry pattern 221 using the actual sintered spots 409 as referencepoints.

One of ordinary skill in the art would immediately recognize that avision system such as those describe herein (405, 408) can be animportant tool in various locations throughout the reel-to-reel machine1. It can be provided before and/or after a specific task to ensure andassist in calibration and alignment. Therefore, there are specificallycontemplated other vision systems throughout the reel-to-reel machine 1and in each of the working modules to perform these functions, eventhough they are not specifically described.

In FIG. 11, the paste 401 can be transferred onto the pad locations 404via a sacrificial liner 406. The sacrificial liner 406 is first preparedby silk-screening the paste 401 onto the sacrificial liner 406 incorresponding spots. Sacrificial liner 406 has a lower surface energy,thereby allowing the paste 401 to stay on the top surface 202 of themetal foil 201, which has higher surface energy.

The metal foil 201 with paste 401 on it now passes under a vision system405 which may include a high-definition camera and/or othervisualization sensors. Vision system 405 detects the locations of eachpaste 401 relative to a reference point. This data is then provided to amicroprocessor which in turn sends a command signal to the laser scanner402. The command signal directs the laser scanner 402 to irradiate theexact locations of these paste 401. In one embodiment, the sinter module400 can be downstream of the laser ablation module 200. This means thecircuitry pattern 221 can be created prior to any sintering takingplace. A vision system 408 which may include a high-definition cameraand/or other visualization sensors may be provided to visualize thecircuitry pattern 221 prior to transferring the paste 401 onto the metalfoil 201. The vision system 408 can visualize and determine the relativelocations of pads 404, relative to a reference point. This data is thencollected and processed by a microprocessor, which then send commandsignals to relevant components of the sintering module 400 to makealignment correction/calibration on the fly. This would ensure thesacrificial liner 406 is accurately aligned with the circuitry pattern221, allowing the paste 401 to accurately attach to pad locations 404.

In another embodiment, the sintering module 400 can be upstream of thelaser ablation module 200. This means the circuitry pattern 221 can becreated by laser ablation after sintering has taken place. Oralternatively, laser scanner 205 that does the laser ablation can alsoconcurrently irradiate the sintering paste 401. Sintering paste 401silkscreened onto designated spots of the sacrificial liner 406 can befirst transferred to an ablated sheet of metal foil 201. A vision system405 which may include a high-definition camera and/or othervisualization sensors may be provided to visualize the relativelocations of the paste 401 on the ablated sheet of metal foil 201. Thisdata is then collected and processed by a microprocessor, which thensend command signals to relevant components of the laser ablation module200, such as the laser scanner 205 in FIG. 5 so that subsequently thelaser scanner 205 would ablate a desired circuitry pattern 221 using theactual sintered spots 409 as reference points.

In some embodiments, any of the first metal foil 601, second metal foil602, top dielectric layer 603, and dielectric layer 604 can be laminatedtogether using any of the herein disclosed lamination method andcomponents. The lamination can occur prior to or after the lasersintering step.

Reel-to-Reel Lamination Device and Method

The novel lamination method relates a process of applying a sheetmaterial onto 1) an ablated metal foil 201 having the circuitry pattern221 and the negative material 223, 2) an unablated metal foil 201, 3) acircuitry pattern 221 with negative material 223 already removed, and/or4) any other material being passed through the reel-to-reel conveyorsystem.

The sheet material can be a 1) UV coverlay 302 (see FIGS. 5, 6, 7, 12,14, and 16), 2) a thermoset coverlay 302 (see FIGS. 5, 6, 7, 13, 15, and17), and/or 4) a plastic laminate 316 as illustrated in FIG. 7. One ofordinary skill in the art would recognize that other appropriatelaminates may also be used using the herein described methods and deviceon the fly. In some instances, all or some components/steps of theherein disclosed lamination method can be used to apply a sacrificialliner to the metal foil 201, such as the sacrificial liner 204 disclosedwhen discussing FIGS. 5 and 7.

Although in some places within this disclosure the lamination processmay be described as a lamination module 500, it should be noted that theword “module” does not limit the related required lamination componentsto take place within a single modular unit. The related requiredlamination components to laminate one sheet material may be dispersed atmore than one locale within the reel-to-reel conveyor system. In otherwords, there may be intervening processes taking place within thelamination process. For example, in FIG. 12, downstream from the niproller 501 but upstream from the UV lamp 503, sintering or laserablation may take place. Also, while some workflow diagrams disclosedherein may indicate only one lamination module 500 in a reel-to-reelmachine 1, it does not limited lamination to only one instance oflamination.

In most embodiments, lamination can take place as part of the hereindisclosed sintering process, laser ablation process, slug-removalprocess, and welding process.

Referring now to FIG. 12, a UV coverlay 302 is applied to the metal foil201 via nip roller 501 and anvil 502. What's shown in FIG. 12 may be adetail drawing of any of the disclosed drawing figures where a UVcoverlay 302 is shown/discussed. Here, the UV coverlay 302 issubsequently passed under a UV lamp 503 to cure the adhesives therebyadhering the UV coverlay 302 to the metal foil 201.

There can be an optional laser scanner 550 somewhere upstream before theUV coverlay 302 is placed on top of the metal foil 201. Laser scanner550 irradiates a laser beam over the top surface 202 of the metal foil201, creating tiny peaks and valleys thereby increasing the surfaceenergy of top surface 202. This can improve adhesion when the UVcoverlay 302 is subsequently laminated to the metal foil 201.

In one embodiment, the laser scanner 550 can indiscriminately irradiatethe entire top surface of the metal foil 201. In another embodiment, thelaser scanner selectively irradiates just the circuitry pattern 221(whether the circuitry pattern 221 has been ablated or has yet to beablated). There can be a vision system 552 to visualize the top surface202 of the metal foil 201, providing data to a microprocessor which inturn signals the laser scanner 550 as to exactly where to irradiate.

Although laser scanner 550 is given a designated part number in thefigures, laser scanner 550 can be any one of the previous describedlaser scanners, if it is physically located upstream from the nip roller501. For example, if the lamination process shown in FIG. 12 is adetailed illustration of what's shown in FIG. 5, then laser scanner 205of FIG. 5 can be the laser scanner 550 of FIG. 12. Similarly, the visionsystem 306 of FIG. 5 can also function as the vision system 552 of FIG.12.

Referring now to FIG. 13, where a thermoset coverlay 302 is applied tothe metal foil 201. Here, somewhere downstream from nip roller 501 andanvil 502 can be a heated nip roller 508 and anvil 509. Heated niproller applies heat and pressure to the thermoset coverlay 302, therebyadhering it to the metal foil 201. Similar to FIG. 12, there can be anoptional laser scanner 550 and an optional vision system 552 to performsimilar functions as in FIG. 12. Also, laser scanner 550 and visionsystem 552 can be any of the upstream laser scanners and vision systems,as previously discussed.

Referring back to FIG. 7, the herein disclosed lamination process can beutilized in at least two places in this figure. Firstly, coverlay 302can be laminated onto the metal foil 201 using any of the hereindisclosed methods. FIG. 7, however, can be a simplified illustrationthus does not show certain details (e.g., a UV lamp or a heated niproller to cure the coverlay are not shown). Secondly, plastic coverlay316 can be laminated onto the metal foil 201 using any of the hereindisclosed methods.

In FIG. 14, further improvements to the lamination process are provided.Here, an air suction nozzle 515 can be provided to minimize retention ofair bubbles between the UV coverlay 302 and the metal foil 201. Suctionnozzle 515 can point directly at the juncture where the UV coverlay 302initially meets the metal foil 201. Suction nozzle 515 can have a linearair intake that corresponds to the widths of the metal foil 201. It canhave a rather flat configuration like a duck bill to extend into thejuncture. The coverlay-metal foil bi-layer is then passed through asealed entrance 512 to a vacuum enclosure 510. Vacuum enclosure 510 mayor may not provide a perfect or near-vacuum condition. Vacuum enclosure510 can provide a negative pressure to whatever multi-layer sheetmaterial that is passed therethrough to drive as much air bubbles out inbetween the layers as possible. In this particular embodiment, thevacuum enclosure has a very small volume and can be comprised of a flatbladder made of two slippery rubber sheets. The flat bladder can have aflexible body and can be connected to a suction source 518, whichcreates a vacuum or near vacuum condition within the flat bladder. Asshown in FIG. 14, the flexible body of the flat bladder sandwiches thebi-layer and leaves very little volume of empty space. Suction providedby the suction source 518 essentially squeezes the two slippery rubberysheets (i.e., flexible body) onto the coverlay-metal foil bi-layer. Thisaction can remove air bubbles from in between the UV coverlay 301 andthe metal foil 201.

The flat bladder can have a transparent skin such that a UV lamp 503 canirradiate through and cure the UV coverlay 302. Alternatively, the UVlamp 503 can be located downstream from the flat bladder to irradiateand cure the UV coverlay 302.

As discussed previously, optional laser scanner 550 can be provided toincrease surface energy of the top surface 202 of the metal foil 201.Similarly, there can be an optional vision system 552 to collect data.

FIG. 15 illustrates a similar set up except the coverlay 302 is athermoset coverlay. Here, instead of a UV lamp, a heated nip roller 508and anvil 509 is used downstream from the vacuum enclosure 510.Alternative to having a heated nip roller 508 and anvil 509, thethermoset coverlay 302 can be cured by a heat source 519 to apply heatto the coverlay-metal foil bi-layer while the bi-layer is still in thevacuum enclosure 510. The heat source 519 can include a CO2 laserscanner (irradiating through transparent vacuum enclosure 510).

FIGS. 16 and 17 provide another two embodiments where the vacuumenclosure 510 has much more volume. In FIG. 16, vacuum enclosure 510 cancontain a UV lamp 503. In FIG. 17, the vacuum enclosure 510 can containa heated nip roller 508 and an anvil 509.

Reel-to-Reel Welding Device and Method

As illustrated in FIGS. 3 and 4, a multi-layer flexible printed circuitcan be created with a reel-to-reel machine 6, 7. Part of this processmay include electrically connecting at least two layers of circuitrypatterns 221 together via a laser welding process.

Referring now to FIG. 18, before metal foil 601 and 602 are weldedtogether at predetermined weld spots 609, the two metal foils 601 and602 are layered together reel-to-reel. The two metal foils 601, 602 areseparated by a dielectric layer 604. There can also be anotherdielectric layer 603 on the top of metal foil 601. These dielectriclayers 603, 604 can be any dielectric sheet material such as a plasticlaminate, a UV laminate, a thermoset laminate, or an adhesive layer.

In one embodiment of the novel welding method, there must be windows 605disposed in dielectric layers 603, 604, thereby exposing thepredetermined weld spot 609. As will be discussed later, there can bevarious ways to create windows 605. The window 605 in the dielectriclayer 604 is especially important because this particular window 605allows the two metal foils 601, 602 to physically touch or come close toeach other after an embossing force is applied to the weld spot 609. Aswill be discussed in FIG. 21, an embossing force can be applied by arotary embossing die 610 through the window 605 against an anvil, or anembossing stamp through the window 605 against an anvil or a flatbed onthe fly.

The embossing force deforms one or both of the metal foils 601, 602. InFIG. 19, top metal foil 601 has been embossed, thereby creating adeformation 612. Deformation 612 now physically touches the bottom metalfoil 602 at the weld spot 609. A laser scanner 620 then irradiates theweld spot 609, effectively welding the two metal foils 601, 602 togetherat the weld spot 609. In another embodiment, the metal foil 601 can bedeformed at the weld spot 609 but not necessarily touching the bottommetal foil 602. The key is to sufficiently deform metal foil 601 so thatit is much closer to the metal foil 602 than had embossing not takenplace.

Referring now to FIG. 21, which illustrates the concept of FIGS. 18 and19 in operation. For purposes of easier illustration, FIG. 21 shows onlythe welding process and does not illustrate other processes such aslaser ablation, sintering, and slug removal.

The operation of FIG. 21 contemplates two metal foils 601, 602 separatedby a dielectric layer 604 with an additional dielectric layer 603 on topof metal foil 601. This configuration is the same as the configurationshown in FIGS. 18 and 19.

Necessary windows 605 on predetermined spots of the top dielectric layer603 can be prepared on the fly by using a rotary die cutter 661 andanvil 662 to make mechanical cuts at desired spots. Waste of the cutmaterial can be removed from the top dielectric layer 603 using asacrificial liner 663. Sacrificial liner 663 can have an adhesivesufficiently strong to adhere to the cut material and roll it away fromthe top dielectric layer 603 in the direction of the shown arrow.

Cutting of the window on the fly can be alternatively performed by a UVlaser scanner or a CO2 laser scanner. Removal of waste material would bethe same as describe above. In some embodiments, the windows are createdprior to layering the first metal foil and/or the top dielectric layer603 to the second metal foil 602. In some other embodiments, the windowsare created after layering the first metal foil and/or the topdielectric layer 603 to the second metal foil 602.

Now that the top dielectric layer 603 has windows 605, the topdielectric layer 603 is transported reel-to-reel around reel 681 to layon top of the first metal foil 601. As discussed elsewhere in thisdisclosure, known visualization or alignment devices can be used to makesure the windows 605 match up with the intended weld spots 609 on thefirst metal foil 601.

Necessary windows 605 on predetermined spots of the middle dielectriclayer 604 can be prepared similarly on the fly. There can be a rotarydie cutter 671 and anvil 672 to make mechanical cuts at desired spots.Waste of the cut material can be removed from the middle dielectriclayer 604 using a sacrificial liner 673. Sacrificial liner 673 can havean adhesive sufficiently strong to adhere to the cut material and rollit away from the middle dielectric layer 604 in the direction of theshown arrow.

Now having windows 605 at desired spots, the middle dielectric layer 604can be layered reel-to-reel around reel 684 to the bottom side of thefirst metal foil 601. Again, known visualization or alignment devicescan be used to match the windows 605 to the intended weld spots 609 onthe first metal foil 601.

This tri-layer continues its travel downstream the reel-to-reel conveyorsystem, and a second metal foil 602 is layered to the bottom side of themiddle dielectric layer 604 via reel 611. Reel 611 can also act as ananvil to the debossing die 610. The debossing die 610 applies adebossing force through the windows 605 and deforms the first metal foil601 as previously described. A Z height setter 690 and a Z heightscanner 691 can be provided to measure the x, y, and z coordinates andmakes proper alignment in real time to ensure proper welding of the weldspots 609.

Laser scanner 620 then irradiates through the windows 605 to the weldspots 609.

What is also not shown in FIG. 22 is any necessary components needed tolaminate these layers together. It should be noted that any of theherein disclosed lamination steps can be implemented in FIG. 22.Dielectric layer 603, 604 can be a UV laminate or a thermoset laminateas described elsewhere in this disclosure.

The operation in FIG. 22 is different from FIG. 21 in that no embossingis used in FIG. 22. Here, only the top dielectric layer 603 has windows605 created (similar to FIG. 21). The middle dielectric layer 604 doesnot have any windows. Laser scanner 620 would irradiate through windows605 of the top dielectric layer 603 and directly onto the weld spots ofthe first metal foil 601. The weld spots of the first metal foil 601would melt and displace and/or burn off some sections of the dielectriclayer 604 directly underneath the weld spots of the first metal foil601. The melted weld spot of the first metal foil 601 would reach theweld spot of the second metal foil 603, making an electrical connection.

In one contemplated embodiment, this middle dielectric layer 604 can bean extremely thin layer of PSA (pressure sensitive adhesive). Thecontemplated PSA thickness is thinner than 10% of the thickness of thetop metal foil 601 (see FIG. 20). The laser can irradiate the intendedweld spots 609 on the first metal foil 601 to displace the adhesivelocally and allow the two metal layers 601, 602 to weld together at theweld spot 609. In one contemplated example, several hundred watts CWfiber laser with galvanometer can be used with a wobble weld technique.

FIGS. 23 and 24 present a similar and more simplified representation asthat shown in FIG. 22. Here, top dielectric layer 603 is not present. Inother scenarios, the top dielectric layer 603 may be present but may ormay not have windows 605 prepared. FIGS. 23 and 24 illustrates anembodiment where laser scanner (such as scanner 620 of FIG. 22)irradiates the intended weld spot 609 and creates molten metal 606 thatdisplaces some part of the middle dielectric layer 604 to weld with thesecond metal foil 602. FIG. 24 shows the molten metal 606 after it iscooled. Molten metal 606 can conduct electricity between the first andsecond metal foils 601, 602, and can have sufficient and desirableproperties (e.g., passing tests on peel force, thermal shock, saltFOG/Salt dunk tests).

FIGS. 25-27 illustrate yet another embodiment where sintering paste 401can be used to achieve the same or similar result as welding. First, alaser scanner (e.g., laser scanner 620 in FIG. 22) irradiates theintended weld spot 609 and creates a hollow space 607. Hollow space 607can also be created by a rotary die (not shown). There may be otherinstances where holes or through-holes may be necessary in any of theherein discloses processes. There can be provided any number of suchlaser scanner or rotary die to create holes or through-holes wheneverand wherever necessary.

Hollow space 607 exposes the second metal foil 602. Sufficient radiationshould be applied here so the intended weld spot 609 so there can beenough displacement of the first metal foil 601 and the middledielectric layer 604, and it should not look like that shown in FIG. 24.Subsequently, sintering paste 401 (see FIG. 26) with metal filler can beplaced into the hollow space 607 via a printer 401 (e.g., silkscreening), or a sacrificial liner 406 as previously described in thenovel sintering process. A vision system such as any of those discussedwithin this disclosure can be used to visualize and ensure accurateplacement of the sintering paste 401. Further downstream from wheresintering paste 401 has been placed into the hollow space 607, thetri-layer as shown in FIG. 26 is transferred reel-to-reel to anotherlaser scanner 642 (see FIG. 28) to irradiate the sintering paste 401 onthe fly. Yet another vision system 641 (see FIG. 28) can be provided toassist the laser scanner 642 for accurate irradiation of the sinteringpaste 401.

In FIG. 28, prior to the laser sintering by laser scanner 642, laserscanner 620 can be performing ablation of the edges 222 of the circuitrypattern 221, a laser welding as described elsewhere in this disclosure,or creating a window 605 meant to receive the sinter paste 401 later.

As previously mentioned, many of the laser scanners and vision systemsdisclosed throughout this disclosure each discussed in the context of adifferent process (e.g., ablation, welding, sintering, separating tiebars, curing adhesives, debonding, applying heat, cleaning off debondingmaterial, laminating a UV laminate) can be the same laser scanner andsame vision system to perform two or more processes, so long as thesequential arrangement of them makes sense. For example, when aparticular workflow is designed to have the process shown in FIG. 28 tooccur immediately before the ablation shown in FIG. 5, vision system 641and laser scanner 642 can perform the added function as vision system205 and laser scanner 306.

Laser scanners have been disclosed in all of the above processes. Thefollowing table provides a summary of the contemplated laser types foreach function:

Specification of Laser and Other Energy Function Sources Laser AblationPulsed Green laser. High-power Pulsed green laser. UV laser. Pulsed Moreprecise green laser. CO2 laser. IR Pulsed Fiber laser (1 um) nano-second, picosecond, and femtosecond Debonding a UV Debonding Violetlaser. Sheet UV laser. Debonding a Thermal debonding CO2 laser. Sheet IRlaser. To Weld Fiber laser. CW fiber laser (several hundred watts usinga wobble weld technique). To Cure an Adhesive in a UV LED (non-laser).Laminate Coverlay UV Laser. Heat Roller. Heat Lamp. IR Lamp. ToIrradiate a Sintering Paste CO2 Laser. Green Laser. Fiber laser. ToClean/Remove Debonding CO2 laser. Material/Debris

Many alterations and modifications may be made by those having ordinaryskill in the art without departing from the spirit and scope of thedisclosed embodiments. Therefore, it must be understood that theillustrated embodiments have been set forth only for the purposes ofexample and that it should not be taken as limiting the embodiments asdefined by the following claims. For example, notwithstanding the factthat the elements of a claim are set forth below in a certaincombination, it must be expressly understood that the embodimentincludes other combinations of fewer, more or different elements, whichare disclosed herein even when not initially claimed in suchcombinations.

The words used in this specification to describe the various embodimentsare to be understood not only in the sense of their commonly definedmeanings, but to include by special definition in this specificationstructure, material or acts beyond the scope of the commonly definedmeanings. Thus if an element can be understood in the context of thisspecification as including more than one meaning, then its use in aclaim must be understood as being generic to all possible meaningssupported by the specification and by the word itself.

The definitions of the words or elements of the following claimstherefore include not only the combination of elements which areliterally set forth, but all equivalent structure, material or acts forperforming substantially the same function in substantially the same wayto obtain substantially the same result. In this sense it is thereforecontemplated that an equivalent substitution of two or more elements maybe made for any one of the elements in the claims below or that a singleelement may be substituted for two or more elements in a claim. Althoughelements may be described above as acting in certain combinations andeven initially claimed as such, it is to be expressly understood thatone or more elements from a claimed combination can in some cases beexcised from the combination and that the claimed combination may bedirected to a subcombination or variation of a subcombination.

Thus, specific embodiments and applications of a novel reel-to-reel FPCfabrication process and its related individual novel steps have beendisclosed. In interpreting both the specification and the claims, allterms should be interpreted in the broadest possible manner consistentwith the context. In particular, the terms “comprises” and “comprising”should be interpreted as referring to elements, components, or steps ina non-exclusive manner, indicating that the referenced elements,components, or steps may be present, or utilized, or combined with otherelements, components, or steps that are not expressly referenced.Insubstantial changes from the claimed subject matter as viewed by aperson with ordinary skill in the art, now known or later devised, areexpressly contemplated as being equivalent within the scope of theclaims. Therefore, obvious substitutions now or later known to one withordinary skill in the art are defined to be within the scope of thedefined elements. The claims are thus to be understood to include whatis specifically illustrated and described above, what is conceptuallyequivalent, what can be obviously substituted and also what essentiallyincorporates the essential idea of the embodiments. In addition, wherethe specification and claims refer to at least one of something selectedfrom the group consisting of A, B, C . . . and N, the text should beinterpreted as requiring at least one element from the group whichincludes N, not A plus N, or B plus N, etc.

What is claimed is:
 1. A method of layering a first layer of circuitrypattern to a second layer of circuitry pattern during manufacturing of amultilayer flexible printed circuit in a reel-to-reel machine, themethod comprising: feeding said first layer of circuitry patternreel-to-reel into the machine; feeding the second layer of circuitrypattern reel-to-reel into the machine; placing a layer of dielectricsheet material on the fly between said first layer and said second layerof circuitry patterns reel-to-reel; simultaneously passing the firstlayer, second layer, and the dielectric sheet material under a laserscanner in the reel-to-reel machine to irradiate a laser beam on apredetermined portion of the first layer of circuitry pattern to weldsaid first and second layers of circuitry patterns together.
 2. Themethod as recited in claim 1, feeding the first layer of circuitrypattern and the second layer of circuitry pattern simultaneously betweena rotary die and an anvil in the reel-to-reel machine, wherein therotary die with protruding features debosses a predetermined portion ofthe first layer of circuitry pattern with sufficient pressure to deformthe predetermined portion into closer proximity to the second layer ofcircuitry pattern.
 3. The method as recited in claim 2, wherein therotary die presses the predetermined portion of the first layer ofcircuitry pattern and the predetermined portion of the second layer ofcircuitry pattern to physically connect to each other.
 4. The method asrecited in claim 3, wherein the laser is a fiber laser.
 5. The method asrecited in claim 3, wherein at least one of the first layer of circuitrypattern and the second layer of circuitry pattern is made of a metalselected from a group consisting of a copper, an aluminum, a nickel, andstainless steel.
 6. The method as recited in claim 5, wherein thedielectric sheet material is a pressure sensitive adhesive (PSA) havinga thickness less than 10% of a thickness of the first layer of circuitrypattern.
 7. The method as recited in claim 6, creating through windowsin the dielectric sheet material prior to placing the dielectric sheetmaterial between said first layer and said second layer of circuitrypatterns.
 8. The method as recited in claim 1, wherein the laser beam issufficient energized for the predetermined portion of the first layer ofcircuitry pattern to melt through the dielectric layer and make physicalconnection to the second layer of circuitry pattern.
 9. The method asrecited in claim 1 further comprising laminating the dielectric sheetmaterial, the first layer of circuitry pattern, and the second layer ofcircuitry pattern together on the fly using an inline vacuum enclosure.10. A method of layering a first layer of circuitry pattern to a secondlayer of circuitry pattern during manufacturing of a multilayer flexibleprinted circuit in a reel-to-reel machine, the method comprising:feeding said first layer of circuitry pattern reel-to-reel into themachine; feeding the second layer of circuitry pattern reel-to-reel intothe machine; placing a layer of dielectric sheet material on the flybetween said first layer and said second layer of circuitry patternsreel-to-reel; simultaneously passing the first layer, second layer, andthe dielectric sheet material under a laser scanner in the reel-to-reelmachine; creating a through-window in the first layer of circuitrypattern; and creating a through-window in the dielectric sheet material.11. The method as recited in claim 10, wherein the through-window of thefirst layer of circuitry pattern and the through-window of thedielectric sheet material correspond to each other thereby creating asingle hollow space, wherein a bottom of the hollow space exposes thesecond circuitry pattern.
 12. The method as recited in claim 11 furthercomprising placing a sintering paste having a metal filler into thehollow space on the fly, wherein the placing step is performed by aprinter or a sacrificial liner.
 13. The method as recited in claim 12,wherein the printer is a silkscreen printer.
 14. The method as recitedin claim 13 further comprising irradiating the sintering paste with alaser to remove a non-metal portion of the sintering paste, leaving themetal filler sintered to both the first layer and the second layer ofcircuitry pattern.
 15. The method as recited in claim 14, wherein thethrough-windows are created in the first layer and the dielectric sheetmaterial after feeding the second layer of circuitry pattern into themachine.
 16. The method as recited in claim 15, wherein thethrough-windows are created in the first layer and the dielectric sheetby a laser scanner.
 17. The method as recited in claim 14, wherein thethrough-windows are created in the first layer and the dielectric sheetmaterial prior to feeding the second layer of circuitry pattern into themachine.
 18. The method as recited in claim 17, wherein thethrough-windows are created in the first layer and the dielectric sheetby a rotary die.
 19. The method as recited in claim 10 furthercomprising laminating the dielectric sheet material, the first layer ofcircuitry pattern, and the second layer of circuitry pattern together onthe fly using an inline vacuum enclosure.